1. Industrial Field of Utilization
The present invention relates to an apparatus for manufacturing a semiconductor and a method for manufacturing a semiconductor device, and more particularly to an apparatus for manufacturing a semiconductor and a method for manufacturing a semiconductor device including reforming an insulating film formed by low temperature CVD.
2. Prior Art
There are a variety of Chemical Vapor Deposition (CVD) methods for forming an insulating film, but a plasma CVD method and a thermal CVD method have been mainly used in recent years. In a very large scale integrated circuit (VLSI), among others a DRAM, an insulating film formed by a plasma CVD method is undesirable since it has inferior step coverage because of refinement and densification and because impurities such as carbon (C) and the like are contained in the formed insulating film. Thus, application of a thermal CVD method superior in step coverage, in particular a thermal CVD method capable of forming a film at a low temperature so as not to exert thermal influence upon other components is attracting attention for forming a refined and densified DRAM.
There have been two thermal CVD methods capable of forming a film at a low temperature as follows:
(1) reaction gas: mixed gas of mono-silane (SiH4)/oxygen (O.sub.2), reaction temperature: 350.degree. to 450.degree. C.
(2) reaction gas: mixed gas of organic silane (TEOS)/ozone (O.sub.3), reaction temperature: 350.degree. to 450.degree. C.
Further, as a CVD method superior in step coverage and capable of forming a film at a low temperature, an optical CVD method for forming a film while subjecting to ultraviolet rays is also attracting attention.
As a rule when a device becomes 1 .mu.m or less, film quality of an interlevel insulating film and the like exerts a big influence upon the device characteristics, and the following problems have been associated with an interlevel insulating film formed by the low temperature CVD method.
Namely, problems affecting reliability by
(1) lowering of dielectric breakdown strength, PA1 (2) increase of leakage current, PA1 (3) corrosion of an Al film, etc. and the like are encountered. The reasons for such problems are that: PA1 (1) the density of the formed insulating film is low, PA1 (2) bonds such as moisture (H.sub.2 O) and Si--OH are contained in the formed insulating film, and PA1 (3) bonds such as Si--H are sometimes contained. PA1 (1) to form a film at the highest possible temperature, PA1 (2) to form a film at the lowest possible growth speed, PA1 (3) to increase O.sub.3 concentration to the highest possible extent in a method using TEOS, and PA1 (4) to anneal a film at the highest possible temperature after film formation. PA1 reaction gas: mixed gas containing mono-silane (SiH.sub.4)/oxygen (O.sub.2), and PA1 temperature: 350.degree. to 450.degree. C., and any one of a SiO.sub.2 film, a PSG film, a BSG film and a BPSG film is formed as the insulating film. PA1 reaction gas: mixed gas containing organic silane (containing alkoxy compound of silicon, siloxane, alkyl-silane and the like)/ozone (O.sub.3), and PA1 temperature: 350.degree. to 450.degree. C., and any one of a SiO.sub.2 film, a PSG film, a BSG film and a BPSG film is formed as the insulating film. PA1 reaction gas: mixed gas containing organic compound such as tantalum (Ta)/ozone (O.sub.3), PA1 temperature: 300.degree. to 450.degree. C., and a Ta.sub.2 O.sub.5 film is formed as the insulating film. PA1 (1) reaction gas: mixed gas (O.sub.3 concentration: 1% in O.sub.2) of organic silane (TEOS)/ozone (O.sub.3), PA1 (2) wafer temperature: 400.degree. C., and PA1 (3) forming speed: 1,000 A/min. PA1 (1) In the case of a mixed gas of oxygen gas/nitrogen gas PA1 (1) Investigation of the minuteness of a CVD SiO.sub.2 film, i.e. etching rate, using an HF water solution, and PA1 (2) investigation of the composition of a CVD SiO.sub.2 film by infrared absorption spectrum PA1 (2) In the case of ammonia gas: PA1 (1) Investigation of the moisture content in a CVD SiO.sub.2 film by an electrochemical method, and PA1 (2) investigation of the composition of a CVD SiO.sub.2 film by infrared absorption spectrum have been performed.
In order to solve such problems, it is required:
However, these countermeasures have limits. For example, when an interlevel insulating film is formed by covering a Al film on a Si substrate, it is undesirable to increase the temperature to 450.degree. C. or higher from the viewpoints of preventing deterioration of the contact between the Al film and the Si substrate and of preventing generation of hillocks and the like. Further, the growth speed cannot be greatly reduced because of need for mass productivity.
Furthermore, there is the problem in the optical CVD method that the growth rate and the film quality of the generated film are lowered because the generated film sticks to the radiating window through which ultraviolet rays are introduced into the chamber while forming a film, producing a blur thereon, and the effect of the ultraviolet rays is thereby reduced. Further, since the original growth rate is low in the optical CVD method, there is also the problem that this method is not suitable for mass production.